defmodule ClacksWeb.FrontendController do
  use ClacksWeb, :controller
  alias Clacks.{Actor, User, Timeline, Repo, ActivityPub, Activity, Object}
  alias ClacksWeb.Router.Helpers, as: Routes
  alias ClacksWeb.Endpoint
  import Ecto.Query

  @public "https://www.w3.org/ns/activitystreams#Public"

  def index(%Plug.Conn{assigns: %{user: user}} = conn, params) do
    user = Repo.preload(user, :actor)

    render(conn, "home.html", %{
      user: user,
      actor: user.actor,
      statuses_with_authors: Timeline.home_timeline(user, params)
    })
  end

  def index(conn, params) do
    Application.get_env(:clacks, :frontend, %{})
    |> Keyword.get(:unauthenticated_homepage, :local_timeline)
    |> index(conn, params)
  end

  defp index(:local_timeline, conn, params) do
    render(conn, "local_timeline.html", %{
      statuses_with_authors: Timeline.local_timeline(params)
    })
  end

  defp index({:profile, nickname}, conn, params) do
    case Actor.get_by_nickname(nickname) do
      %Actor{local: true} = actor ->
        # only local profiles are shown
        render(conn, "profile.html", %{
          actor: actor,
          statuses: actor_statuses(actor, params, only_public: true)
        })

      _ ->
        # otherwise show local timeline
        index(:local_timeline, conn, params)
    end
  end

  defp actor_statuses(actor, params, only_public: only_public) do
    Timeline.actor_timeline(actor, params, only_public)
  end

  def status(conn, %{"id" => id}) do
    current_user = conn.assigns[:user] |> Repo.preload(:actor)

    with %Activity{
           local: true,
           data:
             %{
               "type" => "Create",
               "object" => %{"type" => "Note", "attributedTo" => author_id}
             } = data
         } = activity <- Activity.get(id),
         %Actor{} = author <- Actor.get_by_ap_id(author_id) do
      case conn.assigns[:format] do
        "activity+json" ->
          json(conn, data)

        "html" ->
          render(conn, "status.html", %{
            current_user: current_user,
            status: activity,
            author: author
          })
      end
    else
      nil ->
        case conn.assigns[:format] do
          "activity+json" ->
            conn
            |> put_status(404)
            |> json(%{error: "Not Found"})

          "html" ->
            resp(conn, 404, "Not Found")
        end

      %Activity{local: false, data: %{"id" => ap_id}} ->
        case conn.assigns[:format] do
          "activity+json" ->
            conn
            |> put_status(404)
            |> json(%{error: "Not Found"})

          "html" ->
            redirect(conn, external: ap_id)
        end
    end
  end

  def reply(conn, %{"id" => id}) do
    current_user = conn.assigns[:user]

    with %Activity{
           data: %{
             "type" => "Create",
             "object" => %{"type" => "Note", "attributedTo" => author_id}
           }
         } = activity <- Activity.get(id),
         %Actor{} = author <- Actor.get_by_ap_id(author_id) do
      render(conn, "status.html", %{
        current_user: current_user,
        status: activity,
        author: author
      })
    else
      _ ->
        resp(conn, 404, "Not Found")
    end
  end

  def profile(conn, %{"username" => username} = params) do
    current_user = conn.assigns[:user] |> Repo.preload(:actor)

    case User.get_by_username(username) do
      nil ->
        resp(conn, 404, "Not Found")

      user ->
        user = Repo.preload(user, :actor)

        render(conn, "profile.html", %{
          current_user: current_user,
          actor: user.actor,
          statuses: actor_statuses(user.actor, params, only_public: true),
          following_state: following_state(current_user.actor, user.actor)
        })
    end
  end

  def actor(conn, %{"id" => id} = params) do
    current_user = conn.assigns[:user] |> Repo.preload(:actor)

    case Repo.get(Actor, id) do
      nil ->
        resp(conn, 404, "Not Found")

      actor ->
        render(conn, "profile.html", %{
          current_user: current_user,
          actor: actor,
          statuses: actor_statuses(actor, params, only_public: true),
          following_state: following_state(current_user.actor, actor)
        })
    end
  end

  def follow(conn, %{"id" => id}) do
    current_user = conn.assigns[:user] |> Repo.preload(:actor)

    case Repo.get(Actor, id) do
      nil ->
        resp(conn, 404, "Not Found")

      followee ->
        if current_user.actor.ap_id in followee.followers do
          redirect(conn, to: ClacksWeb.FrontendView.local_actor_link(followee))
        else
          follow = ActivityPub.follow(current_user.actor.ap_id, followee.ap_id)
          ActivityPub.Helper.save_and_federate(follow, current_user.actor)

          conn
          |> put_flash(:info, "Follow request sent")
          |> redirect(to: ClacksWeb.FrontendView.local_actor_link(followee))
        end
    end
  end

  def unfollow(conn, %{"id" => id}) do
    current_user = conn.assigns[:user] |> Repo.preload(:actor)

    case Repo.get(Actor, id) do
      nil ->
        resp(conn, 404, "Not Found")

      followee ->
        unless current_user.actor.ap_id in followee.followers do
          redirect(conn, to: ClacksWeb.FrontendView.local_actor_link(followee))
        else
          new_followers = List.delete(followee.followers, current_user.actor.ap_id)
          changeset = Actor.changeset(followee, %{followers: new_followers})
          {:ok, followee} = Repo.update(changeset)

          follow_activity = follow_activity(current_user.actor, followee)

          changeset =
            Activity.changeset(follow_activity, %{
              data: %{follow_activity.data | "state" => "unfollowed"}
            })

          {:ok, follow_activity} = Repo.update(changeset)

          undo_follow = ActivityPub.undo_follow(current_user.actor.ap_id, follow_activity.data)
          ActivityPub.Helper.save_and_federate(undo_follow, current_user.actor)

          conn
          |> put_flash(:info, "Unfollowed")
          |> redirect(to: ClacksWeb.FrontendView.local_actor_link(followee))
        end
    end
  end

  def search(conn, %{"q" => q}) when is_binary(q) do
    current_user = conn.assigns[:user]

    actor_results =
      case Actor.fetch(q) do
        %Actor{} = actor ->
          [actor]

        _ ->
          []
      end

    status_results =
      with %Activity{
             actor: actor_id,
             data: %{"type" => "Create", "object" => %{"type" => "Note"}}
           } = activity <- Object.fetch(q, true, :activity),
           actor <- Actor.get_by_ap_id(actor_id) do
        [{activity, actor}]
      else
        _ ->
          []
      end

    render(conn, "search.html", %{
      current_user: current_user,
      q: q,
      status_results: status_results,
      actor_results: actor_results
    })
  end

  def search(conn, _params) do
    current_user = conn.assigns[:user]

    render(conn, "search.html", %{
      current_user: current_user,
      q: "",
      status_results: [],
      actor_results: []
    })
  end

  def post_status(conn, %{"content" => _content} = params) do
    current_user = conn.assigns[:user] |> Repo.preload(:actor)

    note = note_for_posting(current_user, params)
    note_changeset = Object.changeset_for_creating(note)
    {:ok, _object} = Repo.insert(note_changeset)

    create = ActivityPub.create(note)
    {:ok, activity} = ActivityPub.Helper.save_and_federate(create, current_user.actor)

    path = Map.get(params, "continue", Routes.frontend_path(Endpoint, :status, activity.id))
    redirect(conn, to: path)
  end

  defp note_for_posting(current_user, %{"content" => content, "in_reply_to" => in_reply_to_ap_id}) do
    with %Activity{data: %{"context" => context, "actor" => in_reply_to_actor}} <-
           Activity.get_by_ap_id(in_reply_to_ap_id) do
      to = [in_reply_to_actor, @public]
      # todo: followers
      cc = []

      ActivityPub.note(
        current_user.actor.ap_id,
        content,
        context,
        in_reply_to_ap_id,
        nil,
        DateTime.utc_now(),
        to,
        cc
      )
    else
      _ ->
        ActivityPub.note(current_user.actor.ap_id, content)
    end
  end

  defp note_for_posting(current_user, %{"content" => content}) do
    ActivityPub.note(current_user.actor.ap_id, content)
  end

  @spec follow_activity(follower :: Actor.t(), followee :: Actor.t()) :: map()
  def follow_activity(follower, followee) do
    # todo: get latest
    query =
      Activity
      |> where([a], fragment("?->>'type'", a.data) == "Follow")
      |> where([a], fragment("?->>'actor'", a.data) == ^follower.ap_id)
      |> where([a], fragment("?->>'object'", a.data) == ^followee.ap_id)
      |> order_by(desc: :inserted_at)
      |> limit(1)

    Repo.one(query)
  end

  @spec following_state(follower :: Actor.t(), followee :: Actor.t()) ::
          :following | :not_following | :pending
  defp following_state(follower, followee) do
    case follow_activity(follower, followee) do
      %Activity{data: %{"state" => "pending"}} ->
        :pending

      %Activity{data: %{"state" => "accepted"}} ->
        :following

      _ ->
        :not_following
    end
  end
end